The present invention relates to a rotary fluid pressure device, and more particularly to a gerotor motor wherein a gerotor set has an externally toothed, balanced rotor member with a first plurality of circumferentially spaced laterally directed fluid paths extending through the rotor and a second plurality of fluid paths being circumferentially interposed between the first plurality of fluid paths for sequentially channeling fluid between one of the first and second axial end faces.
One type of rotary fluid pressure devices is generally referred to as gerotors, gerotor type motors, and gerotor type pumps, hereinafter referred to as gerotor motors. Gerotor motors are compact in size, low in manufacturing cost, have a high-torque capacity ideally suited for such applications as turf equipment, agriculture and forestry machinery, mining and construction equipment, as well as winches, etc. Gerotor motors have gerotor sets which utilize a special form of internal gear transmission consisting of two main elements: an inner rotor and an outer stator.
The inner rotor and the outer stator possess different centers. The inner rotor has a plurality of external teeth which contact circular arcs on the interior of the outer stator when it revolves. An output shaft is either directly connected to the orbiting inner rotor or is connected thereto by a drive link splined at each end. When pressurized fluid flows into a motor, the resistance of an external torsional load on the motor begins to build differential pressure, which in turn causes the inner rotor to rotate in the desired direction via a timing valve. Gerotor motors are typically manufactured in two forms, an internally generated rotor (hereinafter referred to as xe2x80x9cIGRxe2x80x9d) gerotor set or an externally generated rotor (hereinafter referred to as xe2x80x9cEGRxe2x80x9d) gerotor set. The outer stator of both IGR and EGR gerotor sets have one more tooth (N+1 teeth) than the inner rotor (N teeth). When the inner rotor rotates, it also orbits in the opposite direction of rotation with the speed of N times its own rotation.
Due to the flow of pressurized fluid through the gerotor sets, namely into and out of the volume chambers in the gerotor set, the inner rotor tends to have an imbalance of forces acting upon it. This imbalance of forces causes the rotor to tilt to one side during its rotation, resulting in unwanted wear along the surface of the rotor that comes in contact with an adjacent component, e.g. an end cap. Prior art constructions, such as those set forth in U.S. Pat. No. 5,624,248 to Kassen et al. have used an adjacent component, such as a plate, in order to balance the rotor that is tipping in one direction. The plate has hydraulic forces acting on one side, causing it to flex and come in physical contact with the rotor. This contact offsets the differential of forces which tip the rotor, allowing the rotor to rotate uniformly. The present invention uses hydraulically pressurized fluid to balance the rotor without having an extra component that physically contacts the rotor.
Other prior art constructions, such as those set forth in U.S. Pat. No. 4,264,288 to Wxc3xcsthof et al., provide opened/recessed slots on both sides of the hydraulic rotor for balance. This causes the rotor to remain axially aligned within the outer stator during its operation. The present invention differs from this prior art construction by providing two sets of axial through holes for balancing. One set of through holes transfers high pressure fluid, while the other set (which alternates between the first set) of through holes transfers exhaust fluid. This alternation of high pressure fluid and exhaust fluid on each side of the rotor provides the desired balance.
The present invention provides a rotary fluid pressure device comprised of a housing member, a manifold assembly, a gerotor set, an end plate, and a rototably journaled torque transer shaft. This invention overcomes the obstacle of balancing components within the gerotor set during operation of the rotary fluid pressure device.
A feature of the present invention is to provide a rotary fluid pressure device where the housing member defines a fluid inlet port, a fluid outlet port, a first flow passage, a second flow passage and an internal bore. The manifold assembly has a first fluid passage, a second fluid passage, an internal bore, with one side of the manifold assembly adjoining the housing member. The gerotor set has an internally toothed stator member, an externally toothed rotor member disposed within the stator member having an internal bore and a first and a second axial end surface. One of the stator and the rotor members has orbital movement relative to the other member, and the rotor member has a rotational movement relative to the stator. The internal teeth of the stator member and the external teeth of the rotor member interengage to define a plurality of expanding and contracting volume chambers. A first plurality of circumferentially spaced laterally directed fluid paths in the rotor extend through the rotor for fluid connection with the manifold assembly first and second fluid passages. A branch conduit for each of the first plurality of fluid paths adapted for directly connecting respective ones of the first plurality of laterally-directed fluid paths in the rotor to the volume chambers. A second plurality of circumferentially spaced, laterally-directed fluid paths extending through the rotor circumferentially interposed between the first plurality of fluid paths for sequentially channeling fluid between one of the first and second axial end faces. The gerotor set is located between the manifold assembly and the end plate. The rotatably journaled torque transfer shaft is operatively interconnected to the rotor and extends from within the housing member. A plurality of coupling members interconnects the endplate, the gerotor set, the manifold assembly and the housing member.
Another feature of the rotary pressure device is that the first and second plurality of laterally directed fluid paths are substantially axially directed, and that the branch conduits are substantially radially directed. A further feature includes having the first plurality of laterally directed fluid paths in the rotor being located in the rotor between externally toothed members thereof, and having the first plurality of laterally directed fluid paths being substantially laterally directed between the rotor first and second axial ends. Further the first plurality of laterally directed fluid paths could be substantially circumferentially centered between adjacent ones of the rotor externally toothed member thereof.
A further feature of the rotary pressure device is that the second plurality of laterally directed fluid paths is circumferentially centered between the first plurality of laterally directed fluid paths. Also the second plurality of laterally directed fluid paths in the rotor is substantially laterally directed between the rotor first and second axial ends, and wherein the second plurality of laterally directed fluid paths in the rotor is substantially radially aligned with adjacent ones of the rotor externally toothed members. Another feature is wherein the pluralities of the first and second laterally-directed fluid paths are substantially parallel.
Still another feature includes having one of the first and second axial end faces on the rotor having a first plurality of circumferentially spaced recesses located thereon, each of the first plurality of recesses in fluid communication with the first plurality of laterally directed fluid paths. Further, the first plurality of circumferentially spaced recesses can receive fluid for reducing the viscous friction between one of the first and second axial end faces and the end plate. Also, another feature is to minimize the number of circumferentially spaced recesses that do not receive a flowing fluid.
An additional feature of the present invention includes having one of the first and second axial end faces on the rotor having a second plurality of circumferentially spaced recesses located thereon, and each of the second plurality of recesses being in fluid communication with the second plurality of laterally directed fluid paths. Further the second plurality of circumferentially spaced recesses receive fluid for reducing the viscous friction between one of the first and second axial end faces and the end plate. Also, another feature is to minimize the number of circumferentially spaced recesses that do not receive a flowing fluid.
Yet another feature of the present invention includes having the plurality of laterally directed first and second fluid paths in the rotor extend through the rotor from the first axial end surface to the second axial end surface. An added feature of the present invention includes having the rotary fluid pressure device function as one of a hydraulic pump and motor.